Learn Turkish: Gittiğimiz lokantanın atmosferi kesinlikle harikaydı. - The atmosphere of the restaurant that we went to was definitely great.

This is the focus of this lesson! It comes from the verb root git- (to go). We add the participle suffix -dik and the "we" possessive ending -imiz (our). Literally, it acts like "our gone-to [place]". Notice that the d in -dik hardens to a t to match the voiceless t in git-, and the k softens to a ğ because it's followed by a vowel.

Does gittiğimiz describe the restaurant or the atmosphere?

It describes the restaurant. In Turkish, modifying words always come directly before the noun they describe. Gittiğimiz lokanta means "the restaurant that we went to". Then, that entire phrase is used to show ownership of the atmosphere.

Why is there a -nın on lokantanın and an -i on atmosferi?

This is a standard "genitive-possessive" compound, which you learned earlier to show ownership. To say "the atmosphere of the restaurant", lokanta gets the genitive "owner" suffix -nın (the restaurant's), and atmosfer gets the possessive "owned" suffix -i (its atmosphere).

How is the word kesinlikle built?

It is made of three parts: kesin (certain/definite) + -lik (a suffix that makes nouns out of adjectives, like "certainty") + -le (meaning "with"). Literally, it means "with certainty", which translates perfectly to "definitely" or "absolutely".